The Latero-sensory Component of the Dermal Skeleton in Lower Vertebrates and Its Phyletic Significance

Ørvig, T. (Section of Palaeozoology, Swedish Museum of Natural History, Stockholm, Sweden.) The latero-sensory component of the dermal skeleton in lower vertebrates and its phyletic significance. Zool. Scripta 1(3–4): 139–155, 1972.–A latero-sensory component of the dermal skeleton is met with not only in teleostomian fishes, but also in arthrodires, holocephalians (the lateral line canal “rings”), some fossil selachians, bradyodonts and acanthodians, and a few, at least, of the Osteostraci. Although not yet traceable with certainty in the Heterostraci, such a component probably existed even in early stages of vertebrate history. The persistence in the adult of this component as separate ossicles embracing the lateral line canals is surely the result of regression or other modifications of the dermal skeleton in fishes like arthrodires, coelacanthids and actinopterygians, but is apparently a primitive feature in e.g. acanthodians. In discussing the phyletic relations between the latero-sensory and membranous components of the dermal skeleton, it is concluded that these probably were separate formations from the very beginning. A condition (exemplified by certain acanthodians) where separate latero-sensory ossicles of the lateral line canals are surrounded by a mosaic of small scales of membranous origin is presumably that from which the various dermal bone-patterns in lower vertebrates are all derived. A discussion is also included in this paper of the scales and otoliths in acanthodians.     

The Isolated Comet Tail Pseudopodium of Listeria monocytogenes: A Tail of Two Actin Filament Populations, Long and Axial and Short and Random

Listeria monocytogenes is driven through infected host cytoplasm by a comet tail of actin filaments that serves to project the bacterium out of the cell surface, in pseudopodia, to invade neighboring cells. The characteristics of pseudopodia differ according to the infected cell type. In PtK2 cells, they reach a maximum length of ~15 μm and can gyrate actively for several minutes before reentering the same or an adjacent cell. In contrast, the pseudopodia of the macrophage cell line DMBM5 can extend to >100 μm in length, with the bacteria at their tips moving at the same speed as when at the head of comet tails in bulk cytoplasm. We have now isolated the pseudopodia from PtK2 cells and macrophages and determined the organization of actin filaments within them. It is shown that they possess a major component of long actin filaments that are more or less splayed out in the region proximal to the bacterium and form a bundle along the remainder of the tail. This axial component of filaments is traversed by variable numbers of short, randomly arranged filaments whose number decays along the length of the pseudopodium. The tapering of the tail is attributed to a grading in length of the long, axial filaments.

The exit of a comet tail from bulk cytoplasm into a pseudopodium is associated with a reduction in total F-actin, as judged by phalloidin staining, the shedding of α-actinin, and the accumulation of ezrin. We propose that this transition reflects the loss of a major complement of short, random filaments from the comet, and that these filaments are mainly required to maintain the bundled form of the tail when its borders are not restrained by an enveloping pseudopodium membrane. A simple model is put forward to explain the origin of the axial and randomly oriented filaments in the comet tail.

     

Maximal Aerobic and Anaerobic Power Generation in Large Crocodiles versus Mammals: Implications for Dinosaur Gigantothermy

Inertial homeothermy, the maintenance of a relatively constant body temperature that occurs simply because of large size, is often applied to large dinosaurs. Moreover, biophysical modelling and actual measurements show that large crocodiles can behaviourally achieve body temperatures above 30°C. Therefore it is possible that some dinosaurs could achieve high and stable body temperatures without the high energy cost of typical endotherms. However it is not known whether an ectothermic dinosaur could produce the equivalent amount of muscular power as an endothermic one. To address this question, this study analyses maximal power output from measured aerobic and anaerobic metabolism in burst exercising estuarine crocodiles, Crocodylusporosus , weighing up to 200 kg. These results are compared with similar data from endothermic mammals. A 1 kg crocodile at 30°C produces about 16 watts from aerobic and anaerobic energy sources during the first 10% of exhaustive activity, which is 57% of that expected for a similarly sized mammal. A 200 kg crocodile produces about 400 watts, or only 14% of that for a mammal. Phosphocreatine is a minor energy source, used only in the first seconds of exercise and of similar concentrations in reptiles and mammals. Ectothermic crocodiles lack not only the absolute power for exercise, but also the endurance, that are evident in endothermic mammals. Despite the ability to achieve high and fairly constant body temperatures, therefore, large, ectothermic, crocodile-like dinosaurs would have been competitively inferior to endothermic, mammal-like dinosaurs with high aerobic power. Endothermy in dinosaurs is likely to explain their dominance over mammals in terrestrial ecosystems throughout the Mesozoic.     

The Infrabranchial Musculature and Its Bearing on the Phylogeny of Percomorph Fishes (Osteichthyes: Teleostei)

The muscles serving the ventral portion of the gill arches ( = infrabranchial musculature) are poorly known in bony fishes. A comparative analysis of the infrabranchial muscles in the major percomorph lineages reveals a large amount of phylogenetically-relevant information. Characters derived from this anatomical system are identified and discussed in light of current hypotheses of phylogenetic relationships among percomorphs. New evidence supports a sister-group relationship between the Batrachoidiformes and Lophiiformes and between the Callionymoidei and Gobiesocoidei. Investigated data also corroborate the existence of two monophyletic groups, one including the Pristolepididae, Badidae, and Nandidae, and a second clade consisting of all non-amarsipid stromateiforms. New synapomorphies are proposed for the Atherinomorphae, Blenniiformes, Lophiiformes, Scombroidei (including Sphyraenidae), and Gobiiformes. Within the latter order, the Rhyacichthyidae and Odontobutidae are supported as the successive sister families of all remaining gobiiforms. The present analysis further confirms the validity of infrabranchial musculature characters previously proposed to support the grouping of the Mugiliformes with the Atherinomorphae and the monophyly of the Labriformes with the possible inclusion of the Pholidichthyiformes. Interestingly, most hypotheses of relationships supported by the infrabranchial musculature have been advanced by preceding anatomists on the basis of distinct data sources, but were never recovered in recent molecular phylogenies. These conflicts clearly indicate the current unsatisfactory resolution of the higher-level phylogeny of percomorphs.     

Phyletic Relationships of Living Sharks and Rays

A set of hypotheses are developed for the origin of living sharksand rays and the interrelationships of their major groups, usingsome methods of cladistic analysis to relate groups with sharedderived characters. Comparative studies on living sharks andrays combined with new data on fossil sharks suggests that theliving groups ultimately stem from a common ancestral groupof "neoselachian" sharks with many modern characters. Reinterpretationsof "amphistyly" in modern sharks is presented on new data.     

Tadpole Locomotion: Axial Movement and Tail Functions in a Largely Vertebraeless Vertebrate

SYNOPSIS.Tadpoles are exceptional among vertebrates in lackingvertebrae along most of their body axis. Their caudal myotomesare also unusually simple for free-living vertebrates. Thisoverall morphological simplicity, in theory, makes tadpolesgood models for exploring how vertebrates control undulatorymovements. We used electromyography (EMG), high speed ciné,computational fluid dynamics (CFD), and mechanical tissue testingto understand how Rana tadpoles regulate their locomotion. Bullfrog (Rana catesbeiana) tadpoles have several patterns ofmuscle activity, each specific to a particular swimming behavior.Ipsilateral muscles in the tail were active either in seriesor simultaneously, depending on the tadpole's velocity, andlinear and angular acceleration. When R. catesbeiana larvaeswam at their natural preferred tail beat frequency, musclesat the caudal end of their tail were inactive. Mechanical testsof tissue further suggest that the preferred tail beat frequencyclosely matches the resonance frequency of the tail thus minimizingthe energetic cost of locomotion. CFD modeling has demonstrated that the characteristically highamplitude oscillations at a tadpole's snout during normal rectilinearlocomotion do not add to drag, as might be supposed, but ratherhelp generate thrust. Mechanical testing of the tadpole tailfin has revealed that the fin is viscoelastic and stiffer insmall rather than large deformations. This property (among others)allows the tail to be light and flexible, yet stiff enough togenerate thrust in the absence of a bony or cartilaginous skeleton. Many recent studies have documented predator-induced polyphenismin tadpole tail shape. We suggest that this developmental plasticityin locomotor structures is more common in tadpoles than in othervertebrates because tadpoles do not need to reform skeletaltissue to change overall caudal shape. Tadpole tail fins and tip, in the absence of any skeleton, arefragile and often scarred by predators. Based on the high incidenceof tail fin injury seen in tadpoles in the wild, we suggestthat the tadpole tail fin and tip may play an ecological rolethat goes beyond serving as a propeller to help tadpoles staybeyond predators' reach. Those soft tissue axial structures,by failing under very small tensile loads, may also allow tadpolesto tear free of a predator's grasp.     

Social Signals and Behaviors of Adult Alligators and Crocodiles

We compare and contrast the signalling systems and social behaviorsof Alligator mississippiensis, Crocodylus aculus, and Crocodylusmloticus. Our qualitative analysis focuses primarily on thebehaviors of adults during three phases of reproduction: I.Defense of Territory and Courtship, II. Nesting and Incubation,and III. Hatching and Post Hatching. Signals and signal elementsare very similar among the three species. For example, all havevocal, non-vocal acoustic, and visual signals, some transmittedthrough air or water and others through both media. In addition,each species' repertoire is composed of discrete, graded andcomplex signals. A few signals are unique to each species. However,their signalling systems differ in the temporal organizationof the behaviors, and in the relative frequency in which certainfunctional groups of signals occuror in which signals occurin a particular sensory mode. Apparently, the signalling systemsof C. acutus and C. niloticus are more similar to each otherthan either is to the signalling system of A. mississippiensis.The signalling systems of the crocodile species appear to beadapted to open water habitats in which visual signals are advantageousand to high density breeding groups and post-copulatory intersexualcontact. In contrast, the Alligatorsignalling system appearsadapted to a marsh habitat in which vocal signals are likelyfavored and to low density breeding groups.     

Subsurface Musculature of Spiny-Headed Worms (Acanthocephala) and Its Role in Formation of Intercellular Matrix

Published and original data on the organization and ultrastructure of the subsurface (cutaneous) musculature, basal plate, and intercellular matrix of acanthocephalans (spiny-headed worms) were analyzed and reviewed. Similar to flatworms, the basal plate and the intercellular matrix of acanthocephalans proved to be derived from the cutaneous musculature. Specific structure of acanthocephalan cutaneous muscles (the lacunar system, nuclear secretion, specific block arrangement of myofilaments, etc.) allows us to consider it as a special kind of smooth muscle tissue.     

Somatic Musculature of Trichodorus porosus and Criconemoides similis

The somatic musculature of Trichodorus porosus is transversely striated, and that of Criconemoides similis is obliquely striated. The species also differ in configuration of the myofibrils, arrangement of the filaments within the myofibrils, and abundance of sarcoplasmic reticulum. Both species are platymyarian and meromyarian. The muscle cells are composed of myofibrils, sarcoplasm, sarcoplasmic reticulum, and various organelles. The myofibrils of both species contain actin and myosin filaments.     

Ocular Axial Length and Its Associations in Chinese: The Beijing Eye Study

Purpose

To investigate the normative data of ocular axial length and its associations in Chinese.

Method

The population-based Beijing Eye Study 2011 is a cross-sectional study performed in Greater Beijing. The study included 3468 individuals (1963 (56.6%) women) with a mean age of 64.6±9.8 years (range: 50–93 years). A detailed ophthalmic and medical examination was performed. Axial length was measured by optical low-coherence reflectometry.

Results

Axial length measurements were available for 3159 (91.1%) study participants. Mean axial length was 23.25±1.14 mm (range: 18.96–30.88 mm). In multivariate analysis, axial length was significantly associated with the systemic parameters of higher age (P<0.001), higher body height (P = 0.003), higher level of education (P<0.001) and urban region of habitation (P<0.001), and with the ocular parameters of thicker central cornea (P = 0.001), higher corneal curvature radius (P<0.001), deeper anterior chamber (P<0.001), thicker lens (P<0.001), more myopic refractive error (P<0.001), larger pupil diameter (P = 0.018), and higher best corrected visual acuity (P<0.001). It was additionally and negatively associated with the lens vault (P<0.001). In highly myopic eyes, axial length was significantly associated with lower level of education (P = 0.008), more myopic refractive error (P<0.001), and lower best corrected visual acuity (P = 0.034).

Conclusions

Mean ocular axial length in the older adult population of Greater Beijing (23.25±1.14 mm) was similar to the value measured in other urban populations and was higher than in a rural Central Indian population. The association between axial length and older age may potentially be associated with a survival artifact. The association between axial length and body height agrees with the general association between anthropomorphic measures and eye globe size. The association with the level of education and urban region of habitation confirms with previous studies. In contrast in highly myopic eyes, axial length was negatively associated with educational level and best corrected visual acuity.     

The Internal Dynamics of Fibrinogen and Its Implications for Coagulation and Adsorption

Fibrinogen is a serum multi-chain protein which, when activated, aggregates to form fibrin, one of the main components of a blood clot. Fibrinolysis controls blood clot dissolution through the action of the enzyme plasmin, which cleaves fibrin at specific locations. Although the main biochemical factors involved in fibrin formation and lysis have been identified, a clear mechanistic picture of how these processes take place is not available yet. This picture would be instrumental, for example, for the design of improved thrombolytic or anti-haemorrhagic strategies, as well as, materials with improved biocompatibility. Here, we present extensive molecular dynamics simulations of fibrinogen which reveal large bending motions centered at a hinge point in the coiled-coil regions of the molecule. This feature, likely conserved across vertebrates according to our analysis, suggests an explanation for the mechanism of exposure to lysis of the plasmin cleavage sites on fibrinogen coiled-coil region. It also explains the conformational variability of fibrinogen observed during its adsorption on inorganic surfaces and it is supposed to play a major role in the determination of the hydrodynamic properties of fibrinogen. In addition the simulations suggest how the dynamics of the D region of fibrinogen may contribute to the allosteric regulation of the blood coagulation cascade through a dynamic coupling between the a- and b-holes, important for fibrin polymerization, and the integrin binding site P1.     

Infanticide by Males and Its Implications

Infanticide by Males and Its Implications. Carel P. van Schaik and Charles H. Janson. eds. Cambridge: Cambridge University Press, 2000.569 pp.     

The Tail Gland of Canids

The tail gland of canids is a hepatoid glandular organ surrounded and penetrated by powerful hair erector muscles squeezing out its lipoprotein secretion onto the skin surface. The gland is most developed in solitary species (Arctic, red, and corsac foxes) where it is represented by powerful glandular layer with large secretion containers—cisterns. It is less developed in the jackal; there are cisterns but glandular lobes do not merge into a layer. In the raccoon dog, wolf, and domestic dog the gland is composed of small lobes without cisterns. Hepatoid glands of the tail gland are represented by two histological variants distinguished by the presence or absence of hydrophobic lipids in the secretory cells. The excretory ducts are formed by lipid transformation of the cellular bands.     

The Skeleton and Musculature of the Male Genitalia in Platypezidae (Diptera)

Entomological Review - The musculature of the male genitalia of Platypezidae (Diptera) is described for the first time. The hypandrium in members of the subfamilies Platypezinae and Callomyiinae...